Magnetic core circuit



July 27, 1965 J SWEENEY 3,197,745

MAGNETIC CORE CIRCUIT Filed April 13, 1960 OUTPUT 3/4 SET FULL SET WITH FLUX SHUNT JOSEPH P. SWEENEY M. mm 9 ATTORNEYS United States Patent Office 3,197,745 Patented July 27, 1965 3,197,745 MAGNETIC CORE CIRCUIT Joseph P. Sweeney, Harrisburg, Pa., assignor to AMP Incorporated, Harrisburg, Pa., a corporation of New Jersey Filed Apr. 13, 1960, Ser. No. 22,036 3 Claims. (Cl. 340-474) This invention relates to an improved memory arrangement using a core of material having square-loop magnetic characteristics, and more particularly a multi-aperture core.

An object of this invention is to provide an analog memory device having improved ability to remember and reproduce any one of a number of discrete signal levels.

A further object is to provide such a device wherein the read-out is non-destructive but with less chance of false operation than has previously been possible.

Still another object is to provide a device of this kind which is simple and inexpensive to build.

These and other objects will in part be understood from and in part pointed out in the foliowing description.

A multi-aperture magnetic core (also called a MAD) is toroidal in form with a large center aperture and one or more minor apertures through its body. Now, one of the important advantages of such a core is that, in accordance with known techniques, the flux stored in the core, which flux is proportional to a given signal level to be remembered, can be read-out or sensed without destroying the information being remembered. This is accomplished by passing an interrogate current through a minor aperture to switch flux locally around it without switching flux around the major aperture.

It is proposed to use a MAD core to store any of various levels of flux proportional to an analog signal. But as will be explained in detail hereinafter this complicates the non-destructive read-out operation. Under certain conditions, the read-out signal is the same for two supposedly different memory conditions. This, of course, is unacceptable. The present invention solves this difficulty.

In accordance with the invention, in one specific embodiment thereof, a MAD core is provided with an auxiliary minor aperture, in addition to a read-out aperture, and this auxiliary aperture threaded with a short-circuited conductor. The effect of this shorted conductor is to prevent undesired changes in the flux through that portion of the core encircled by the conductor. This, as will be explained shortly, eliminates ambiguity in sensing the stored flux in the core.

A better understanding of the invention together with a fuller appreciation of its many advantages will best be gained from the following description given in connection with the accompanying drawings wherein:

FIGURE 1 is a diagram of a MAD core analog memory circuit embodying features of the invention;

FIGURE 2 is a schematic representation of a prior art MAD core illustrating the flux when the core is in its reset or clear state;

FIGURE 3 shows the core of FIGURE 2 when it is A set;

FIGURE 4 shows this core when it is A set; and

FIGURE 5 shows the core of FIGURE 1 embodying the invention when the core is fully set.

The analog memory circuit shown in FIGURE 1 comprises a MAD core 12 which is made of a squareloop magnetic ferrite material, such as General Ceramics type number 5209. This core has a central or major aperture 14, a minor read-out aperture 16 and a minor auxiliary aperture 18. Each minor aperture, for the core shown, is placed midway between the inner and outer edges of the body of the core so that substantially equal flux passes through the portions of the core on each side of the aperture.

The central aperture of core 12 is threaded by a clear winding 20 and by a set winding 22, each of which is adapted to be energized at appropriate times by a respective current having approximately the waveform indicated. The amplitude of the clear current is made sufilcient so that at the end of this current the core will be left saturated with flux oriented, for example, in the clockwise direction. This will be called the clear or reset state of the core. Thereafter, a momentary set current is applied to winding 22 to reverse part of the previous flux, the magnitude of the set current determining what fraction of the flux will be reversed. Thus the core can be set with some flux oriented in the counter-clockwise direction, the amount of the set flux being proportional to a signal level to be remembered. As will be explained, the maximum amount of flux which can be set in the counterclockwise direction in this circuit is /2 of the total clear flux.

To sense the counter-clockwise or set flux stored in core 12, read-out aperture 16 is provided with an interrogate winding 24, which is adapted to be energized by an alternating current of sufficient amplitude to switch the flux, if any is switchable, locally around aperture 1 6. Any flux which is so switched induces in an output winding 26 a corresponding alternating voltage proportional to the flux being switched back and forth around aperture 16. As will be understood better later on, the amount of flux switchable around aperture 16 by the interrogate current is determined by the amount of flux set in the counter-clockwise direction.

Auxiliary minor aperture 18 of core 12 is threaded by a shorted conductor 28 encircling the outer leg 29 of the core. The efl'ect of this conductor is to eliminate ambiguities in reading-out the flux stored in the core. The electrical and magnetic action of conductor 28 will be understood more fully in connection with FIGURES 2-5.

FIGURE 2 shows a conventional MAD core 30 with its flux in the reset condition as indicated by the arrows 32. In this condition normally it is impossible to set any flux locally around the minor aperture 34, corresponding to aperture 16 of core 12, since the fluxes on each side of this aperture are in the same direction.

FIGURE 3 shows core 30 in its A set condition. Here, there are three units of clockwise reset flux 32 and one unit of counter-clockwise, or set flux 36. An interrogate current through minor aperture 34 can therefore reverse one unit of flux. But, this same result is obtained for the core in its set state as shown in FIGURE 4. Though there are now three counter-clockwise or set units of flux 36 and one reset unit 32, nonetheless the same amount of flux, one unit, can be reversed around the minor aperture 34. Thus the read-out signal obtained for the set condition will be the same as for the A set condition. This is intolerable in a true analog memory.

FIGURE 5 shows core 12 in its fully set condition and illustrates how the invention prevents ambiguity in readout. Core 12, in addition to read-out aperture 16, has auxiliary minor aperture 18 which is threaded by shortcircuited conductor 28. When a set current is applied by winding 22 to reverse flux 32, the sudden attempt to change the flux in log 29 encircled by this conductor induces a heavy current in the conductor, its resistance being relatively low. Therefore, the set current even at its maximum value is unable to reverse the direction of flux in leg 29. Accordingly, after being fully set the core is left in the flux condition shown in FIGURES. Of course, for smaller than maximum set currents, proportionally less flux will be oriented in the counter-clockwise direction. The presence of shorted conductor 28 thus makes it impossible to orient the flux around read-out aperture 16 so that there is an ambiguous situation as illustrated for example in FTGURES 3 and 4.

Since, conductor 28 has at least some resistance, it is possible under long term conditions to cause the flux in leg 2E to change. However, it is assumed that the set current has far too short a duration to do this. On the other hand, a long duration reset current can be used to advantage in this circuit to insure that all of the flux in leg 29 is returned to or maintained in reset condition.

The above description of the invention is intended in illustration and not in limitation thereof. Various changes may occur to those skilled in the art and these may be made without departing from the spirit or scope of the invention as set forth.

I claim:

1. An improved magnetic core memory comprising: a toroidal core of magnetic material and having a first minor aperture and a second minor aperture, conductor means threading said first minor aperture to inhibit switching of flux in a portion of said core, means to set the flux in said core to a desired level, means to reset the fiux in said core to a cleared condition, means threading said second minor aperture to switch flux locally thereabout, and means threading said second minor aperture to sense the flux stored in said core.

2. An improved magnetic core memory circuit comprising: a toroidal core of magnetic material, said core having at least two minor apertures through it, read-out winding means threading one of said minor apertures, set Winding means on said core for setting the flux therein to a desired value, clear Winding means on said core for resetting the flux therein, a low-resistance conductor means threading the other of said minor apertures and encircling a portion only of said core, the said read-out winding means further including a first conductor adapted to be energized by an alternating current, and a second conductor coupled to the first conductor by magnetic flux in said core.

3. A magnetic core circuit comprising a toroidal magnetic core having a major and two minor apertures, a short-circuited conductor having a given resistance threading one of said minor apertures, read-out winding means coupled to the other of said minor apertures, first current pulse means to set said core with flux in one direction, and second current means to reset said core with flux in the other direction, an interrogate winding threading the said other of said minor apertures to switch flux locally thereabout to provide an output signal on said read-out winding means, the said short-circuited conductor serving to limit the flux set in the one direction to substantially half the flux capacity of the magnetic core.

References Cited by the Examiner UNITED STATES PATENTS 2,284,406 5/42 DEntrernont 340--l74 2,939,117 5/60 Brown 340-174 3,077,582 2/63 Bauer 340174 OTHER REFERENCES Pages 303-311, June 1955, publication: The Transfiuxor-A Magnetic Gate With Stored Variable Setting, RCA Review.

IRVING L. SRAGOW, Primary-Examiner.

EVERETT R. REYNOLDS, Examiner. 

2. AN IMPROVED MAGNETIC CORE MEMORY CIRCUIT COMPRISING: A TORODIAL CORE OF MAGNETIC MATERIAL, SAID CORE HAVING AT LEAST TWO MINOR APERTURES THROUGH IT, READ-OUT WINDING MEANS THREADING ONE OF SAID MINOR APERTURES, SET WINDING MEANS ON SAID CORE FOR SETTING THE FLUX THEREIN TO A DESIRED VALUE, CLEAR WINDING MEANS ON SAID CORE FOR RESETTING THE FLUX THEREIN, A LOW-RESISTANCE CONDUCTOR MEANS THREADING THE OTHER OF SAID MINOR APERTURES AND ENCIRCLING A PORTION ONLY OF SAID CORE, THE SAID READ-OUT WINDING MEANS FURTHER INCLUDING A FIRST CONDUCTOR ADAPTED TO BE ENERGIZED BY AN ALTERNATING CURRENT, AND A SECOND CONDUCTOR COUPLED TO THE FIRST CONDUCTOR BY MAGNETIC FLUX IN SAID CORE. 